Outboard motor cooling and exhaust system

Abstract

An outboard motor features a v-type internal combustion engine having a generally vertically extending crankshaft. Exhaust gases from combustion chambers are routed through a set of exhaust manifolds positioned within the valley defined by the two banks of cylinders. The exhaust flow is merged within a passage formed in the cylinder block prior to passing the exhaust flow into a passage formed within an exhaust guide plate to which the engine is mounted. The merged flow passage is positioned to allow a compact outboard motor construction. The motor also features a cooling pattern by which the exhaust manifold runners, the exhaust manifold, the cylinder head, the valley and the cylinders are cooled in that order.

What is claimed is:  
     
       1. An outboard motor comprising an internal combustion engine, an exhaust guide plate being positioned generally below said internal combustion engine and including an exhaust guide passage, said internal combustion engine comprising a generally vertically extending crankshaft and a cylinder block having a pair of cylinder banks inclined relative to one another, each of said pair of cylinder banks including at least one cylinder, a cylinder head assembly enclosing said cylinder, said cylinder head assembly comprising at least one exhaust port and at least one corresponding exhaust runner, said exhaust runner being in selective communication with said exhaust port and being formed between said exhaust port and an exhaust manifold such that said engine includes two exhaust manifolds that extend in generally vertical directions, a pair of connecting exhaust conduits communicating with said exhaust manifolds and extending toward said cylinder block, said cylinder block also having a pair of passages formed therein that are in registry with said connecting exhaust conduits, said passages merging within said cylinder block into an exhaust discharge, and said exhaust discharge being coupled to said exhaust guide passage, wherein said engine further comprises a flywheel attached to said crankshaft and having an outer diameter, said exhaust discharge of said cylinder block being positioned within said cylinder block such that said outer diameter overlaps at least a portion of said exhaust discharge when viewed from the top. 
     
     
       2. The outboard motor of claim  1 , wherein said exhaust discharge is formed vertically lower than axes of said cylinders. 
     
     
       3. The outboard motor of claim  2 , wherein said exhaust discharge is positioned generally between said cylinder banks. 
     
     
       4. The outboard motor of claim  3 , wherein said engine further includes at least one water jacket and said exhaust manifolds are partially defined by at least one cover including sad water jacket. 
     
     
       5. The outboard motor of claim  4 , wherein said outboard motor includes a propulsion unit and a shaft that rotates at least a portion of said propulsion unit and that is powered by said crankshaft, said exhaust discharge being positioned along a central bisecting plane extending in a generally vertical direction through said shaft. 
     
     
       6. The outboard motor of claim  4 , wherein said exhaust manifold is defined by at least one exhaust manifold cap that is positioned to a rear facing side of said engine. 
     
     
       7. The outboard motor of claim  4 , wherein said cylinder block further comprises two rear corners and said cylinder block and said exhaust guide are bolted together at said two rear corners and in a position along a central bisecting plane extending in a generally vertical direction through said crankshaft. 
     
     
       8. The outboard motor of claim  4 , wherein a juncture of said exhaust discharge and said exhaust guide passage is sealed. 
     
     
       9. The outboard motor of claim  8 , wherein said juncture between said exhaust discharge and said exhaust guide passage consists of a one-to-one piping connection. 
     
     
       10. An outboard motor comprising a first cylinder bank and a second cylinder bank, said first cylinder bank and said second cylinder bank being inclined relative to one another and jointly forming at least a portion of a cylinder block, a crankcase cover connected to a portion of said cylinder block and defining a crankcase chamber, a generally vertically extending crankshaft extending through said crankcase chamber between said crankcase cover and said cylinder block, a first cylinder head assembly being attached to said first cylinder bank and a second cylinder head assembly being attached to said second cylinder bank, a first exhaust manifold being connected to said first cylinder head assembly, a second exhaust manifold being connected to said second cylinder head assembly, an exhaust passage being formed in said cylinder block and comprising a first branch, a second branch and a convergent portion that combines said first branch and said second branch, and said first and second exhaust manifolds separately communicating with said first and second branches respectively, wherein said first and second exhaust manifolds communicate with said first and second branches through a first connection passage and a second connection passage respectively, wherein said first and second connection passages are formed within said first cylinder head assembly and said second cylinder head assembly respectively, wherein said first and second exhaust manifolds are at least partially formed in said first and second cylinder head assemblies respectively. 
     
     
       11. The outboard motor of claim  10 , wherein said first and second exhaust manifolds also are at least partially defined by a first exhaust manifold cap and a second exhaust manifold cap. 
     
     
       12. The outboard motor of claim  11 , wherein said first exhaust manifold cap and said second exhaust manifold cap each includes a cooling jacket extending therethrough. 
     
     
       13. The outboard motor of claim  10 , wherein said first and second exhaust manifolds are positioned between said first and second cylinder head assemblies. 
     
     
       14. The outboard motor of claim  13  further comprising a flywheel attached to an upper end of said crankshaft, said flywheel having an outer diameter, said cylinder block exhaust passage being positioned such that said outer diameter overlaps at least a portion of said cylindea block exhaust passage when viewed from the top of the motor. 
     
     
       15. The outboard motor of claim  13  further comprising a starter motor and a flywheel, said flywheel being connected to said crankshaft and said starter motor selectively driving said flywheel, said crankshaft being interposed between said cylinder block exhaust passage and said starter motor and a distance between said crankshaft and said starter motor being substantially the said as a distance between said crankshaft and said cylinder block exhaust passage when viewed from the top of the motor.